Plenty of criticism to be found about Win95/98.
The control panel and menus upon menus upon menus were not very user friendly. The design was built around low-res CRT screens, which very negatively affects modern screens. Hitboxes were often small, especially for the mice at the time. Commonly used UI elements such as the start menu lacked tons of features we take for granted now (searching in the start menu, for example). Icons were low-res and not always clear, though they were made excellently with more care than any other facet of any modern piece of software I can think of. Navigation controls were severely limited, simple things like breadcrumb navigation simply wasn't invented yet.
Windows XP fixed a lot of small issues found in the Win9x/Win2k UI styling. It had its own problems, but going back to the 9x days is not always an improvement.
It says a lot that I find the 9x style so much easier to use than the "modern" flat designs. It's like we're back in the middle of DOS text characters all over again, having UI elements execute actions after you've guessed about what they might do.
As for a modern take on old ideals, the SerenityOS design is an amazing combination of Win9x/Win2k ideas and modern controls. ReactOS is also used to have a new take on the old style, but that has been modernized to Win10-like menu bars in recent releases.